In the existing broadband wireless communication system, in order to control the power consumption of the User Equipment (UE, or referred to as terminal), the Discontinuous Reception (DRX) technology is used.
The DRX refers to that the terminal stops monitoring the Physical Downlink Control Channel (PDCCH) during a certain time. The DRX is divided into two types: one is IDLE DRX, that is, the discontinuous reception when the terminal is in the IDLE state. When being in the IDLE state, there is no Radio Resource Control (RRC) connection or the dedicated resources of the user, so the IDLE DRX is mainly used for monitoring the calling channel and the broadcast channel; so long as a fixed cycle is defined, it can achieve the purpose of the discontinuous reception. However, if the terminal monitors the user data channel, it must firstly enter the connection state from the IDLE state. Another type is the Active DRX, that is the DRX when the terminal is in the RRC-CONNECTED state, which can optimize the system resource configuration, and more important thing is that it can save the power consumption of the terminal, and it can achieve the purpose of saving the power consumption of the terminal while not need to let the terminal enter the RRC_IDLE state. For example, for some non-real-time applications (web browsing, instant messaging, etc.), there is always a certain time when the terminal does not need to uninterruptedly monitor the downlink data, and does not need to carry on the relevant processing either, and the DRX can be applied to such a scene. In addition, because there is the RRC connection under the Active DRX state, the speed that the terminal turns into the state of monitoring the downlink data is very fast.
The base station transmits the DRX configuration parameter to the UE through the RRC connection reconfiguration signaling.
There are some timers in the DRX, and these timers are described hereinafter; wherein, all time is based on the subframe, that is, ms is used as the unit:
1, continuous working timer (On Duration Timer)
the time that the terminal keeps awake after waking up from the DRX each time, and the terminal will search for the PDCCH within this cycle of time.
2, stop timer (Inactivity Timer)
the time that the terminal keeps active after successfully decoding the PDCCH originally transmitted by the Hybrid Automatic Repeat Request (HARQ) every time when the terminal is awake, that is, the time that the terminal needs to keep active after receiving the PDCCH indicating one original transmission (rather than retransmission) of the UL/DL.
3, total working timer after once waking up (Active Timer)
the total time that the terminal keeps awake after waking up from the DRX; in this time period, the terminal monitors the PDCCH, including all states causing the terminal to be Active, for example, the DRX cycle begins “On Duration”, or receiving the originally transmitted PDCCH, or monitoring the retransmission, etc.
If the DRX is configured, then the Active Time includes the following time: the time that the On Duration Timer, the Inactivity Timer, the DRX Retransmission Timer and the media access control (MAC) Layer Contention Resolution Timer run; or, there is a Scheduling Request (SR) which is already transmitted to the PUCCH and is in the hanging up state (that is, the scheduling request is not satisfied); or, there is the uplink authorization for one hanging up HARQ, and there are data in the corresponding HARQ buffer; or, after the non-compete random accessing, it receives the random access response message successfully, and now there should be a PDCCH transmitted to the terminal to indicate a new transmission, but the PDCCH has not been received yet, and the terminal must be in the Active state at this moment.
4, HARQ round trip timer (HARQ RTT Timer)
the minimum interval time, expected by the terminal, that the downlink retransmission (DL Retransmission) is arrived, that is, the terminal does not need to care when the retransmission will arrive for the moment; so long as the timer is overtime, the terminal needs to be in the waking up state.
5, DRX Retransmission Timer
the time that the terminal expects to receive the DL Retransmission, that is, it needs so much time to receive the downlink retransmission.
6, DRX Cycle Length
once the DRX Cycle length is configured/reconfigured, it will be fixed, and will not change because the Active Time is greater than the On Duration.
The execution process of the existing DRX mainly includes: if the short DRX cycle is used, then it checks whether the current subframe satisfies the formulae: [(SFN*10)+subframe number] modulo (short DRX Cycle)=(DRX StartOffset) modulo (short DRX Cycle); wherein, the SFN is a system frame number, the subframe number is the number of the subframes, the short DRX Cycle is the short DRX cycle, the DRX StartOffset is the DRX starting offset, and the modulo represents modeling; if the long DRX cycle is used, then it checks whether the current subframe satisfies the formulae: [(SFN*10)+subframe number] modulo (long DRX Cycle)=DRX StartOffset; wherein, the long DRX Cycle is the long DRX cycle; when one of the above two conditions is satisfied, then it starts the On Duration Timer and at this moment the terminal starts to monitor the PDCCH. When the HARQ RTT Timer of the subframe (the shortest time of expecting retransmission) is overtime, the retransmission may come; if there are the data which are not decoded successfully (that is, the above data are failed to be received and the data need to be retransmitted) in the soft buffer of the HARQ process at this moment, then the DRX Retransmission Timer is started to start monitoring the PDCCH retransmitting associated data. If the DRX command media access control layer control information unit (the DRX command MAC CE) is received, which means that the eNB requires the terminal to enter the sleep state, and it will stop the On Duration Timer and the DRX Inactivity Timer at this moment, but will not stop the timer associated with the retransmission for requiring the terminal to continue monitoring the content of the retransmission. When the DRX Inactivity Timer is overtime or the DRX command MAC control information unit is received, if the short DRX cycle is configured, then the DRX short Cycle Timer is started or restarted, and the short DRX cycle is used; otherwise; the long DRX cycle is used; if the DRX short Cycle Timer is overtime, then the long DRX cycle is used.
The starting point of setting two-stage DRX Cycle is thinking that the possibility of transmitting the data again once after one data transmission process is finished is relatively high, so a short DRX cycle is set to deal with the kind of probability; when there is no data to transmit during several short DRX cycles, this illustrates that the data transmission is finished really, and it may enter into the deep sleep state; in this way, the cooperation of the long and short cycles can reach better DRX effect.
The above-mentioned are the definitions of different timers in the DRX mechanism and the DRX execution procedure explained by taking the LTE system as examples. The DRX mechanism can also be applied to other systems, such as the Universal Mobile Telecommunications System (UMTS) or the Global System of Mobile communication (GSM), etc. The specific execution detail has some difference, but the general procedure is similar.
With the popularization of the intellectual mobile phone and the diversification of the intellectual software and application, the optimization demand on the terminal power consumption becomes a problem required to pay more and more attention to at present. For the present hot application, such as, the instant communication software, the generation of its data has the characteristic that it is random and the data bulk is less, that is, each data transmission (usually one data transmission includes a plurality of application layer data packets produced continuously each time, for example, it will download a plurality of embedded objects to click the webpage link once) includes less serial data packet, and the interval time of earlier and later transmitting the data is longer; when the current DRX mechanism replies to this type of business, after one data transmission is finished, there actually are no any data required to be transmitted (because of the interval time for transmitting the next data is longer) in the several short DRX cycles performed by the DRX mechanism); because the short DRX cycle needs the UE to consume more power as to the long DRX cycle, the DRX technology cannot be well adapted to the instant communication business. And also because the related technology cannot distinguish the instant communication business and other data business (except the speech business), if the number of times of configuration of the short DRX cycle is reduced simply, then it is possible that it is not adapted to other types of data business. If the network dynamically adjusts the configuration of the short DRX cycle through measuring the data regular, it will cause extra signaling expenses of the RRC configuration, and influence the efficiency of the system.